Makefile: disable cJSON support when building without math support

Signed-off-by: Thiago Macieira <thiago.macieira@intel.com>

.github/workflows/build.yml

@@ -128,7 +128,7 @@ jobs:
         eval "$EVAL"
         # FIXME: remove -Wno-error-line below.
         export CFLAGS="$CFLAGS -Wno-error=implicit-function-declaration"
-        make OUT=.config -s -f Makefile.configure configure | tee .config
+        make OUT=.config V=1 -s -f Makefile.configure configure && cat .config
         make -k \
             CFLAGS="$CFLAGS -march=native -g1 -Wall -Wextra -Werror" \
             CPPFLAGS="-DNDEBUG -DCBOR_ENCODER_WRITER_CONTROL=-1 -DCBOR_PARSER_READER_CONTROL=-1" \

Makefile.configure

@@ -15,8 +15,9 @@ PROGRAM-freestanding += int main() {}
 CCFLAGS-freestanding = $(CFLAGS)
 
 PROGRAM-cjson  = \#include <stdlib.h>\n
+PROGRAM-cjson += \#include <math.h>\n
 PROGRAM-cjson += \#include <cjson/cJSON.h>\n
-PROGRAM-cjson += int main() { return cJSON_False; }
+PROGRAM-cjson += int main() { double d = NAN; return cJSON_False; }
 CCFLAGS-cjson = -I$(dir $(MAKEFILE))src
 PROGRAM-system-cjson = $(PROGRAM-cjson)
 CCFLAGS-system-cjson = -lcjson